DCS Or Legacy As The Primary Control System?


Hello everyone, I’m hoping to tap into the vast amount of experience contained by the members of the OGR forum for some advice and hope this is the right area to post this question.          



I am in the early stages of construction on a new layout and I currently have some limited experience with TMCC and Legacy as I have used it on a previous one.

On the old layout I had two long loops of track about 46 feet long each.  I ran a 12 gauge bus wire with feeders every 8 to 10 feet.  The Legacy system was connected with a TMCC base and I had 1 TPC 400 with 2 180W Bricks powering each loop so I could run command and conventional.


For the new layout I would like to incorporate the MTH DCS system as well as TMCC / Legacy.  I have zero experience with DCS and do not currently own any MTH engines.  I purchased Barry Broskowitz book on DCS and have read it (It’s a very informative book) but I’m more of a hands on guy when it comes to learning and without having the system in hand it makes it difficult for me to completely understand.


The new layout will be Atlas track and switches with some Ross switches as well.


1st Question:

From a control standpoint which system is better suited to be the primary system for controlling switches and accessories as well as trains?  Would legacy be a better choice or would the DCS system be a better choice?


I’m attaching an RR-Track file and a BMP of the track plan to this post as that may be a contributing factor in deciding which system is better suited to be used as the primary one. 


2nd Question:

From looking at the track plan would you guys think it is not a good candidate for DCS based on the fact that it follows around the walls and through a few rooms?  Anyone have any experience with installing DCS on a large around the walls layout?


From what I have read the DCS system is not well suited for bus wiring and since my layout follows around the walls and through a few rooms, I don’t think DCS would work well if installed that way. 


When I started planning this layout and was only thinking of using Legacy / TMCC I was going to wire with a bus and divide the layout into 4 power districts using one TPC 400 with two 180W bricks for each district .  I was planning on incorporate toggles in small panels for block wiring near the location of the tracks being blocked on the layout.   


3rd Question:

Does Legacy / TMCC work well if this is wired in a star pattern for DCS?  Or is that not really an issue for Legacy / TMCC.  Does DCS run conventional as well as the TPC 400’s do? 


I only own a couple of old Lionel and a few newer Williams conventional engines.  I was thinking of eventually converting them to TMCC so maybe I should just go command only at this point anyway. 


I know I will have more question as I progress with this so any advice or insight would be greatly appreciated.



AI Draft Track Plan 18 Electrical

A. Infinito

President & Chief Operating Officer


Serving The Basement.



Original Post

Your layout looks really great for running.


1st - Both systems are good.  My personal preference was the MTH DCS system.  The MTH system requires fewer components to control track, switches, and accessories.  Legacy train control runs side by side with the DCS system.  With DCS you can use most postwar power supplies and most "bricks".


2nd - My track plan with MTH DCS (around the walls) works great with a buss system, not star wiring.  I do use the Engineered Filters with my older TIUs.  See layout here.  The arrows on each section map are clickable for the photo tour.


3rd - I don't know.  All my track can be switched to run conventional with the MTH Z4000 Remote.  That's just my personal preference for conventional running.


Susan thanks for the reply, your layout is fantastic!  How many TIU's do you have on the layout? 


I've been trying to figure out how many I might need based on my layout design and the type of wiring I decide to go with.



A. Infinito

President & Chief Operating Officer


Serving The Basement.


These are not answers; just my thoughts:


1)  Susan is correct; if you plan to control all your switches and accessories through command control, the DCS system will have fewer components and be cheaper overall.  The AIU, for $110, can control 10 switches and 10 accessories.  Lionel's ASC will only control 4 switches OR 8 accessories, for $115.  For my layout, Legacy will be about the same cost as DCS because all my Ross switches use DZ-2500 switch machines which have built in TMCC capability, so I don't need to buy any ASC or SC-2 to control the switches.  Additionally, I don't plan to have many accessories that will be controlled through the handheld so I don't need to buy more than one AIU or ASC for that.


2)  The DCS forum has a discussion on DCS usage on a large club layout.  Do a search for it and it may help answer your questions on this.  Basically, those engineered filters Susan mentioned seem to do a good job.


3)  Cannot answer the conventional part of the question, although if you incorporate DCS from the start the overall wiring diagram should be simpler since you can control conventional through the TIU.   Legacy should not be affected by the wiring method chosen (star or bus), but the area where you have track directly over track on a lower level may need some additional grounded wires between the levels to limit signal interference.



Questions 1 & 2 are covered above.


Q3; Conventional operation with DCS;

Each TIU has 4 channels:

2 Fixed Channels require the transformer powering of the channel be used to control the voltage, they are normally only used for Command control with 18VAC flowing.

2 Variable channels will adjust the voltage to the track allowing conventional operation or work the same as the 2 Fixed channels (you can switch back and forth with the remote).

Conventional mode works well with lots of engines, BUT some engines exhibit fast takeoffs using DCS track control. THE TIU starts track voltage at 5VAC and notches up from there.

Engines that run well on less than 5VAC may start off too fast (esp if they have little or no load).

This can be reduced by Inputting less than 18VAC to the Variable channels.

This will allow ANY engine to run decently in Conventional operation.

Alternately a set of Parallel opposed Diodes installed in the engine can drop volts to the motor without affecting other parts of the engine.

This is great for older engines that run fast with dim lights & poor smoke.



You have created a very auspicious plan and you are asking good questions.

If you like, come over to see my layout in Carmel, New York. My layout is quite large,

uses Atlas O track and switches, controls all switches using DCS and runs Legacy as

well as DCS. I'll be glad to show you as well as give you a summary of how it all works.

We're the Munoz Lines.


For DCS, Barry Broskowitz and Marty Fitzhenry are two of the best sources to be found.

If you like, send me an e-mail and we can chat.



Passengers will please refrain, This train's got the disappearin' railroad blues...

Thanks for the replies everyone! I'm now leaning toward DCS as the primary system.  Eliot, thanks so much for the invitation I really appreciate it. I just may take you up on your offer!

A. Infinito

President & Chief Operating Officer


Serving The Basement.


I would go with whatever system runs the most of the engines you have If you are planning to convert most of your engines to TMCC then go Legacy. If you have MTH then start DCS. Remember to run your TMCC engines with DCS you will need to buy a TMCC system anyway. You may b e able to chase down a old TMCC base, but you will be better off just getting the Legacy to begin with


I can see challenges on your layout for both of them



A. Infinito,


I also have DCS as the primary control system of my layout, and then added Legacy to run Legacy and TMCC engines and cranes.


I have 57 switch tracks, 45 Atlas and 12 Ross with DZ1000, and all are operated via five AIU's in parallel with toggle-switches at a traditional control panel. I get by with just five AIU's (50 switch track ports) because 11 pairs of switch tracks are crossovers connected in parallel, so overall I use only 46 AIU switch track ports.


I have two TIU's and use their eight output channels to power eight distribution blocks, each of which powers six tracks for a total of 20 power districts and 28 track blocks. I refer as power districts the sections of main line track that are isolated from each other. I have two mains, and each is divided into 10 such districts. The other 28 track blocks are sidings and spurs. (BTW, I learned all of this, and the terminology, from Rich Melvin's excellent video on DCS, as well as from Barry's book.)


After I had the layout track complete and the basic wiring done, I added Legacy, and this could not have been simpler! All it took was to run one wire from the Legacy base to the outside rail that was more convenient to access, and that was it! I run both DCS and Legacy with no problems. (But I do not run any conventional, though.)


Good luck!


Happy O-Gauge Railroading!

  Alexander Müller

See My Mostly Completed Layout Here

OGR Articles: Runs 256, 263, 267, 292

OGR  forum member since 26 January 2008

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